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/*

 * mkdisk.c -- make an empty physical disk

 */

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <stdarg.h>

#define SECTOR_SIZE             512

#define MIN_NUMBER_SECTORS      100

#define SECTORS_PER_MB          ((1 << 20) / SECTOR_SIZE)

#define DATA_BYTE               0xE5

void error(char *fmt, ...) {

  va_list ap;

  va_start(ap, fmt);

  fprintf(stderr, "Error: ");

  vfprintf(stderr, fmt, ap);

  fprintf(stderr, "\n");

  va_end(ap);

  exit(1);

}

void usage(void) {

  fprintf(stderr, "Usage: mkdisk <file name> <n>[M]\n");

  fprintf(stderr, "       <n>: decimal number of sectors\n");

  fprintf(stderr, "       if 'M' appended: megabytes instead of sectors\n");

  fprintf(stderr, "       (sector size is always %d bytes)\n", SECTOR_SIZE);

  exit(1);

}

int main(int argc, char *argv[]) {

  FILE *dskFile;

  int numSectors;

  unsigned char sectorBuffer[SECTOR_SIZE];

  int i;

  if (argc != 3) {

    usage();

  }

  numSectors = atoi(argv[2]);

  i = strlen(argv[2]) - 1;

  if (argv[2][i] == 'M') {

    numSectors *= SECTORS_PER_MB;

  }

  if (numSectors < MIN_NUMBER_SECTORS) {

    error("this disk is too small to be useful (minimum size is %d sectors)",

          MIN_NUMBER_SECTORS);

  }

  dskFile = fopen(argv[1], "wb");

  if (dskFile == NULL) {

    error("cannot open file '%s' for write", argv[1]);

  }

  fprintf(stdout,

          "Creating disk '%s' with %d sectors (around %d MB)...\n",

          argv[1], numSectors,

          (numSectors + SECTORS_PER_MB / 2) / SECTORS_PER_MB);

  for (i = 0; i < SECTOR_SIZE; i++) {

    sectorBuffer[i] = DATA_BYTE;

  }

  for (i = 0; i < numSectors; i++) {

    if (fwrite(sectorBuffer, SECTOR_SIZE, 1, dskFile) != 1) {

      error("write error on file '%s', sector %d", argv[1], i);

    }

  }

  fclose(dskFile);

  return 0;

}